Pheromones

ABSTRACT

Compounds which are β-farnesene derivatives obtainable as a Diels-Adler adduct of β-farnesene and a dienophile or by a modification of such an adduct in a manner as defined herein are of value in pest control, particularly in the control of aphids.

This invention relates to derivatives of (E)-β-farnesene, to theproduction of (E)-β-farnesene and of the derivatives, and to their usein insect control.

The sesquiterpene, (E)-β-farnesene (1), is the main component of thealarm pheromone of many species of aphid and it has been suggested thatthis compound might be used in aphid control. ##STR1## The suggestionshave included the use of the alarm pheromone to increase theeffectiveness of insecticidal sprays by increasing mobility of aphidsand thereby increasing contact with the toxicant, the dispersion ofaphids from their feeding sites by treating these sites with thepheromone and the restriction of virus spread by aphids through similartreatment. Whilst experiments have suggested that the use of thepheromone in conjunction with insecticides might have some potentialvalue, the value of its application to feeding sites is severely limitedby the tendency of aphids to recolonise the feeding sites fairly rapidlycoupled with the volatility of (E)-β-farnesene and its very highsensitivity to aerial oxidation.

The instability of many pheromones has presented a long standing problemto their use in pest control and many methods have been employed forformulating pheromones in order to counter their instabilty. We haveused a quite different approach and have found that it is possible toprepare derivatives of (E)-β-farnesene which are active and which aresufficiently stable to be used in approaches to aphid control such asthe restriction of virus spread where the instability of (E)-β-farnesenerenders the parent compound itself of little value.

Accordingly the present invention comprises a β-farnesene derivativewhich is obtainable as a Diels-Alder adduct of β-farnesene and adienophile or by modification of such an adduct in a manner as definedhereinafter.

Whilst the activity of the natural pheromone resides in the (E) or transcompound it is not necessarily the case with the compounds of thepresent invention that adducts of (Z)-β-farnesene are devoid ofworthwhile activity. It will be seen from the Examples that the adductsare for convenience prepared from a mixture of (E)-and (Z)-β-farnesenein which the (E) form is the major component so that the (E) derivedcompound therefore predominates in the mixture of Diels-Alder adductsobtained. However, although the invention is discussed hereinafter withparticular reference to the (E)-β-farnesene adducts it is possible thatthe (Z) derived compounds may contribute some activity to the mixture.

In the Diels-Alder reaction, the terminal 1,3-diene system of the(E)-β-farnesene reacts with the dienophile forming an (E)-β-farnesenederivative of formula (2) ##STR2## wherein A represents the residue ofthe dienophile. A wide variety of electron deficient dienophiles may beused in forming (E)-β-farnesene derivatives according to the presentinvention. The most common forms of dienophile contain a carbon-carbondouble or triple bond, a nitrogen-nitrogen double bond or anitrogen-oxygen double bond with at least one electron withdrawing groupattached to at least one of the multiply bonded carbon or nitrogenatoms. In practice dienophiles are often used in which each multiplybonded atom carries such a group. Examples of such electron withdrawinggroups include various groups comprising a carbonyl group linked toanother organic group, such as groups CO.OR in which R is a monovalentaliphatic hydrocarbon group which may, for example, contain a group Rsuch as methyl, ethyl, decyl, octadecyl or other groups of this typedescribed hereinafter; aryloxycarbonyl groups, for examplephenoxycarbonyl; groups C.OR in which R is as just defined and whichmay, for example, contain alkyl groups as just described; aryl carbonylgroups, for example phenylcarbonyl; carboxyl; formyl; andcarbonyloxycarbonyl, carbonyliminocarbonyl or other divalent groupswhich are joined to both of the multiply bonded atoms. Specific examplesof such dienophiles which are of some particular interest are diethylmaleate, didecylmaleate, diethyl acetylene dicarboxylate, didecylacetylene dicarboxylate, diethyl azodicarboxylate and other relateddiesters containing two ester groups CO.OR or one ester group CO.OR anda second CO.OR' as discussed hereinafter: azodicarboxylic acid,particularly maleic acid and especially acetylene dicarboxylic aciddiesters containing ester groups derived from dihydroxy alcohols of thetype HO--(CH₂ CH₂ O)_(n') H in which n' is preferably an integer asdiscussed hereinafter; 1,2-bis-(tridecanoyl)-ethylene,1,2-bis-(tridecanoyl)-acetylene and related diketones; acetylenedicarboxylic acid, maleic acid and particularly maleic anhydride;maleimide and derivatives thereof in which the nitrogen atom issubstituted by a group CO.OR in which R may be as referred to above andparticularly the compound N-methoxycarbonylmaleimide; methylethenylketone and acrolein (propenol). Other examples of suitable dienophilesinclude alk-2-yn-1-oic acids, R.C.tbd.C--CO₂ H, which may contain groupsR as referred to above, and discussed in more detail hereinafter,particularly saturated groups of 1 to 18 carbon atoms or even more, forexample the compound hex-2-yn-1-oic acid; cinnamic acid esters andacrylic acid esters which may both contain groups CO.OR as referred toabove and discussed in more detail hereinafter; mesityl N-oxide;N-phenyltriazolidinedione; and 1,4-benzoquinone and2,3-diazo-1,4-benzoquinone and derivatives thereof in which the benzenering carries one or more substituents. In other dienophiles, which areof somewhat lesser interest, the electron withdrawing grouping mayinstead contain a cyano group, a nitroso group or an ether group as, forexample, in tetracyanoethylene, nitrosobenzene and alkoxy olefines suchas vinyl methyl ether, respectively.

Other, less common forms of dienophile, which are however of particularinterest in the context of the present invention, include compoundscontaining a sulphur atom joined by double bonds to one or particularlymore electronegative atoms, for example two atoms such as oxygen atoms,and compounds containing a phosphorus atom joined to one or particularlymore electronegative atoms, for example three atoms such as halogenatoms. Specific examples of such dienophiles are sulphur dioxide andphosphorus tribromide.

It will be appreciated that when the dienophile is of a type whichcontains two multiply bonded atoms, of which at least one carries aselectron withdrawing group, then the dienophile residue A which is shownin formula (2) above will correspond to the dienophile but with thenumber of bonds between the two atoms reduced by one and with each atominstead possessing a free valency for bonding of the residue A into asix membered ring. With a dienophile of the type which contains an atomsuch as oxygen or phosphorus carrying a lone pair of electrons notinvolved in the attachment to these atoms of other, electronegative,atoms then the dienophile residue A will correspond to the dienophilebut with these lone pair electrons providing the free valency forbonding of the residue A into a five membered ring.

As indicated above, the Diels-Alder adduct may not only be used directlyin aphid control but may also in some cases first be converted to aderivative of the adduct before use. In such derivatives the dienophileresidue A shown in formula (2) and/or the remainder of the ringcontaining A is modified by one, or where appropriate by a combinationof two or more of the modifications (for example 2 and 3 or 2, 3 and 4)listed below, the compounds derivable by such modifications beingincluded by the present invention.

1. Reduction of an alkoxycarbonyl group or groups to a methylol ormethyl group.

2. Hydrolysis of one or more ester groups to a carboxy group(particularly groups --CO.O-alkyl), the product being isolated as thefree acid or as a salt.

3. Decarboxylation with the replacement of one or more carboxyl groupsof hydrogen. The groupings --N(CO₂ H)--N(CO₂ H)-- and --N(CO₂alkyl)--N(CO₂ H)-- will undergo spontaneous decarboxylation to give thegroupings --NH--NH-- and --N(CO₂ alkyl)--NH--, respectively. Thegrouping --NH--NH-- may also undergo further spontaneous reaction, forexample to --N═N-- followed by ring cleavage, so that hydrolysis of onlyone or two vicinal N-alkoxycarbonyl groups is preferred in a reaction toproduce a modification of type 2.

4. Oxidation either to introduce an additional separate double bond intothe ring formed by the Diels-Alder reaction or to convert this ring toaromatic form. Such oxidation is preferably applied to carbocyclicrings, for example after following a reaction to produce a modificationof type 3 in which two vicinally disposed carboxyl groups aredecarboxylated. For the reasons indicated under 3 application of such anoxidation to N-heterocycles is more difficult, particularly when areaction --N(CO₂ H)--N(CO₂ H)--→--NH--NH-- is involved, but oxidation ofboth cyclohexene and cyclohexadiene ring systems to benzene, forexample, is possible.

5. Modification of an alkoxycarbonyl group or groups to effectreplacement thereof by a group ##STR3## in which S may be O or NR² and Tmay be NR² R³ or (when S is NR³) may be OR², R² and R³ each beingseparately selected from hydrogen, and alkyl and aryl groups, forexample lower alkyl groups (i.e. of one to four carbon atoms) andphenyl.

6. Modification of a trihalophosphorus group to a group ##STR4## inwhich R₁ represents an --O-alkyl or --S-alkyl group containing, forexample, lower alkyl groups such as methyl or ethyl, and R₂ and R₃together represent either a carbonyl or thiocarbonyl group,respectively.

Other modifications include:

7. Modification of the imino group of a grouping --CO--NH--CO-- toreplace the hydrogen atom of that group by a group --CO.OR wherein R isa monovalent aliphatic hydrocarbon group, for example an alkyl group andparticularly a lower alkyl group such as methyl or ethyl or other groupsR as discussed herein, optionally followed by replacement of the group--CO.OR by a group --D--CO.OR¹ in which D is a divalent aliphatichydrocarbon group, for example of one to four carbon atoms, particularlyan alkylene group such as methylene and R¹ is a salt forming cation, forexample an alkali metal cation, hydrogen or a monovalent aliphatichydrocarbon group, for example a group R such as described herein.

8. Modification of groups --CO.N(CO.OR).CO-- produced directly as aDiels-Alder adduct to form a grouping --CO.N(D.CO.OR¹)CO-- as describedabove.

9. Modification of an acid anhydride group, ##STR5## to give thedicarboxy compound, ##STR6## either as the free di-acid or preferably asa salt thereof, for example an alkali metal salt such as the di-sodiumsalt. Such a modification is applicable especially to the adduct frommaleic anhydride.

In the following discussion of compounds according to the presentinvention it will be apparent from the nature of the group A, comparewith formula (2), what dienophiles have been used to prepare thecompounds and what further modifications of adducts have been effectedaccording to the previous discussion.

One group of compounds according to the present invention which is ofparticular interest is represented by the formula ##STR7## wherein Xrepresents a 4,8-dimethyl-3,7-nonadienyl, Y, Y', Y" and Y'" eachrepresent hydrogen or any two of these which are adjacent represent thesecond bond of a carbon-carbon double bond joining the positions towhich they are attached and the other two represent hydrogen, or Y andY' together and Y" and Y'" together each represent such a second bond ofa carbon-carbon double bond, the ring being aromatic, and R¹ and R² eachseparately represent hydrogen or monovalent aliphatic hydrocarbon group.

One group of compounds according to the present invention which is ofparticular interest is represented by formula (3): ##STR8## wherein Xrepresents a 4,8-dimethyl-3,7-nonadienyl group, Y, Y', Y" and Y'" eachrepresent hydrogen or any two of these which are adjacent represent thesecond bond of a carbon-carbon double bond joining the positions towhich they are attached and the other two represent hydrogen or Y and Y'together and Y" and Y'" together each represent such a second bond of acarbon-carbon double bond, the ring being aromatic, and R and R' eachseparately represent an aliphatic hydrocarbon group.

In preferred compounds of formula (3) the ring is aromatic, orparticularly all four groups Y, Y', Y", Y'" are hydrogen or, moreespecially, Y' and Y'" are hydrogen and Y and Y" represent the secondbond of a carbon-carbon double bond. The groups R' and R" may eachrepresent a different aliphatic hydrocarbon group but are mostconveniently the same. The aliphatic hydrocarbon group may be branchedor unbranched and saturated or unsaturated. The presence of a highdegree of branching may lead to a reduction in activity but branching ofthe type which involves the carbon atom attached to the group --CO.O--,i.e. the ester group being derived from other than a primary alcohol andparticularly a secondary alcohol, may be of value in conferring upon thecompound a greater level of stability in the field. Similarly, whilstgood levels of activity are obtainable with saturated aliphatichydrocarbon groups (alkyl groups), the presence of unsaturation in R andR', for example one double bond i.e., alkenyl, may increase thedispersibility of the compound without any disadvantageous effect andmay even lead to an improvement in activity.

The range of size of the aliphatic hydrocarbon groups R (and R') can bequite considerable ranging from 1 up to 18 or 20, or even as high as 28or 30, depending on whether the chain is branched and/or unsaturated,and on the exact nature of the activity against aphids which thecompound is required to exhibit. When R and R' are selected fromunbranched alkyl groups a range of size of C₈ to C₁₆ may conveniently beused to produce compounds of formula (3) effective in preventing thesettling of aphids. Above this range the activity tends to change to anarrestant one causing aggregation rather than repulsion of the aphids,although such activity may itself be of value as discussed hereinafter.A preferred range within that of C₈ -C₁₆ is C₈ -C₁₄ or C₈ -C₁₂,compounds in which R and R' are each unbranched alkyl groups of 9, 10 or11 carbon atoms being of particular interest, the level of repellentactivity generally increasing from 9 to 10 and from 10 to 11 carbonatoms, and then falling thereafter. When R and R' are selected fromunsaturated aliphatic hydrocarbon groups, settling prevention activitymay be maintained up to higher carbon values so that, for example, thecompound having R=R'=oleyl is of higher repellent activity than that inwhich R=R'=octadecyl, showing dispersant rather than arrestant activity.However, although some difference as to preferences within the broadrange of carbon size may occur as to whether R is saturated,unsaturated, straight chain or branched, the preferences indicated abovefor straight chain alkyl groups may often be generally applied.

Specific examples of groups from which R and R' may be selected areoctyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,hexadecyl, heptadecyl, octadecyl, oleyl, 1-methyldecyl, 1-methylnonyl,1-methyloctyl, 5-decenyl, 10-undecenyl, 5-undecenyl, and 6-undecenyl.

The comments made above in relation to the groups R and R' in compoundsof formula (3) apply generally to compounds of formulae (4) and (5)which are also of some interest: ##STR9## the symbols R, R', Y, Y", Y',Y'" and X having the meanings indicated above. In the case of compoundsof formula (4) a compound having a group COR with R containing aparticular number of carbon atoms may show properties more closelyrelated to the compound formula (3) having a group CO.OR with R of oneless carbon atom, the group being of closely similar size due to thepresence of the extra oxygen atom. As indicated above, however, thebroad preferences mentioned generally apply.

Other diester compounds include compounds of formula (6) and (7):##STR10## wherein X, Y, Y', Y" and Y'" are as defined above, Vrepresents a group --(CH₂ CH₂ O)_(n') H in which n is an integerconveniently from 1 to 9 or 10 and preferably 1 to 5 or 6, and Wrepresents the same or different group --(CH₂ CH₂ O)_(n') H or a group Ras defined above. Preferred compounds have groups Y, Y', Y" and Y'" asdiscussed above, groups V and W which are each --(CH₂ CH₂ O)_(n') H andconveniently the same group of this type, and values of n of 2, 3 or 4.Compounds of formula (6) are of greater interest than those of formula(7).

Another group of compounds of especial interest are those of formula(6): ##STR11## wherein X Y, Y', Y" and Y'" are as above, B is --O--,--NH-- or >N--D--CO₂ R¹ in which D represents a direct bond between thenitrogen atom and the group CO₂ R or a divalent aliphatic hydrocarbongroup, and R¹ represents hydrogen, a salt cation or a group R as above.The interest in these compounds resides particularly in the fact thatthey may exhibit at least some degree of systemic activity. Among thesecompounds B is preferably oxygen or especially a group >N--D--CO₂ R¹,particularly when D is of one to four carbon atoms, for examplemethylene, and/or when R¹ is hydrogen or a salt cation, and Y, Y', Y"and Y'" are preferably each hydrogen.

A range of specific examples of compounds per se which are includedwithin the scope of the present invention is shown below, the linearpart of the residue of (E)-β-farnesene [an(E)-4,8-dimethyl-3,7-nonadienyl group] being shown in full in the firstformula and by the symbol X thereinafter, n representing an integer from1 to 18, particularly 9, 10 or 11 in the first two formulae and 10, 11or 12 in the seventh formulae, and n' representing an integer from 1 to10, particularly 2, 3 or 4. ##STR12##

(E)-β-farnesene provides a convenient starting material for thepreparation of the compounds according to the present invention. Apreferred route to (E)-β-farnesene is the dehydration of (E)-nerolidol(9) or of (E,E) or (Z,E)-farnesol (10): ##STR13## However, theprocedures which have previously been described in the art for effectingdehydration, such as the use of phosphorus oxychloride/pyridine with(E)-nerolidol and potassium hydroxide with (E,E)- and (Z,E)-farnesolhave varous disadvantages such as low yields coupled with difficultiesin large scale operation, and considerable contamination withalternative dehydration products so that in the case of nerolidol, forexample, a high proportion of α-farnesenes often results on dehydration.These problems are compounded by the fact that the commerciallyavailable forms of nerolidol and farnesol are mixtures of isomers, i.e.(E)- and (Z)-nerolidol and (Z,Z)-, (Z,E)-, (E,Z)- and (E,E)-farnesol,only certain of which are capable of yielding the desired(E)-β-farnesene on dehydration. We have therefore turned our attentionto this problem and have discovered a new process for the production of(E)-β-farnesene which is superior to the processes described in theliturature.

According to the present invention a process for the production of(E)-β-farnesene from (E)-nerolidol comprises passing (E)-nerolidolthrough heated aluminium oxide.

Whilst it is possible to apply the process to purified (E)-nerolidol, itis more convenient in practice to use commercially available nerolidolcontaining a mixture of (E)- and (Z)-nerolidol as the starting materialand the process of the present invention is sufficiently successful forthe resulting contamination with (Z)-β-farnesene to be acceptable sincethe dehydration product obtained contains a relatively low proportion ofisomeric hydrocarbon contaminants, very little of the α-farnesenes beingproduced. The yield of β-farnesenes which can be obtained fromcommercial nerolidol by the process of the present invention typicallylies in a range from 40% to 70% with a proportion of the (E) isomer tothe (Z) isomer in the mixture which is typically about 2:1.

In order to obtain yields of the level just quoted, the aluminium oxide(alumina) used should be substantially free of active acidic sites. Theyields obtained with commercial neutral alumina are thus only very lowand whilst commercially available basic alumina may be employed, it hasbeen found that enhanced yields result from using commercially availablealumina, particularly neutral alumina, and exposing this before use to abase, particularly a nitrogenous base such as ammonia or especially anorganic base including mono, secondary and particularly tertiary amines.The bases which may be used include linear aliphatic bases such astriethylamine or analogues thereof containing three, similar ordifferent, alkyl groups (e.g. lower alkyl groups) cyclic aliphatic basessuch as cyclohexylamine, carbocyclic aromatic bases such as aniline, andboth non-aromatic and aromatic heterocyclic bases such as pyrrolidineand pyridine.

The present invention thus includes a process for the production of(E)-β-farnesene from (E)-nerolidol which comprises passing (E)-nerolidolthrough heated aluminium oxide treated with a nitrogenous base.

The passage of the nerolidol through a mass of alumina means that thenerolidol and particularly the farnesene produced therefrom is incontact with the alumina for only a relatively short period, theresidence time perhaps being of the order of only about one minute, ascompared with the more conventional type of reaction carried out in avessel in which reactants and products are maintained together for sometime. It is believed that the rapid completion of the reaction followedby the rapid removal of the volatile farnesene from the reaction sitemay be responsible for the high yields which may be obtained.

Conveniently the nerolidol is passed through a heated column of alumina,for example by the application of a vacuum or the use of a stream ofinert gas such as nitrogen. Alternatively the nerolidol may be allowedto drip on to the hot alumina in such a column which is maintained undervacuum. In the preferred procedure which uses a base to treat neutralalumina, the base is conveniently passed through the column just priorto its use for the dehydration, conveniently again employing vacuum oran inert gas stream. The alumina may conveniently already be at anelevated temperature when treated with the base, for example the sametemperature as is used for the dehydration. This temperature is selectedin order to avoid pyrolysis and cyclization resulting from the use oftoo high a temperature and to avoid lack of reaction or loss of yieldresulting from too low a temperature. The dehydration is preferablycarried out using a temperature in the range from 125° to 350° C.,conveniently 180° to 220° C., for example about 200° C. Preferably thenerolidol is in the vapour state and may conveniently be contacted withthe heated alumina under a vacuum which enables the nerolidol to bevaporised at a lower temperature than otherwise, a convenient vacuumbeing 10τ or less, particularly 1τ or less, for example 0.1 to 0.2τ.

The product from the dehydration may conveniently be purified bychromatography on an adsorbent such as silica gel with a hydrocarbonsolvent such as hexane as an eluant to remove any oxygen-containingimpurities or alternatively may be used directly. Althoughchromatography, for example on silver nitrate, may be used to remove the(Z)-isomer and other, minor, isomeric hydrocarbon impurities from the(EI)-β-farnesene, it is preferred in practice to use the (E), (Z)mixture as such. (E)-β-farnesene is susceptible to aerial oxidation(particularly as the product produced according to the present inventionis substantially free of α-farnesenes) and if storage under nitrogen isnot used then even at -20° C. in the dark oxidation will cause a 20%loss of activity after seven days storage. Accordingly, the compound ispreferably stored under nitrogen in sealed ampoules and in use is thengenerally as active as the natural pheromone allowing for the percentageof the active ingredient (E)-β-farnesene which it contains.

Preparation of (E)-β-farnesene derivatives according to the presentinvention conveniently involves reaction of (E)-β-farnesene with theparticular dienophile under conditions similar to those described in theliterature for the reaction of that dienophile with other dienes such asbuta-1,3-diene, etc. Diels-Alder reactions generally require a varietyof conditions ranging from simple admixture at room temperature toheating at sometimes quite elevated temperatures. As would be expected,the Diels-Alder reaction of (E)-β-farnesene proceeds more readily withsome dienophiles than others, examples of dienophiles which are moredifficult to react including tetracyanoethylene, 1,4-benzoquinones andalkoxy olefines. In such cases, techniques known in the art for use inconnection with difficult Diels-Alder reactions may be employed such asthe use of Lewis acids, for example boron trifluoride, withalkoxyolefines such as vinyl methyl ketone.

Accordingly the present invention also includes a method for preparing(E)-β-farnesene derivatives as described hereinbefore which comprisestreating (E)-β-farnesene with a dienophile to effect a Diels-Alderreaction between these reactants with the formation of a Diels-Alderadduct which may optionally be modified by further reaction as describedhereinbefore.

Where the desired derivative involves modification of a Diels-Alderadduct, appropriate conditions are used to effect the modification.Thus, referring to the modifications listed hereinbefore the followingtypes of reaction may be employed in the various cases.

1. The reactions >N--CO₂ alkyl→>N--CH₃ and ##STR14## may conveniently beeffected using a metal hydride reagent such as lithium aluminiumhydride.

2. Hydrolysis may conveniently be effected using an alkali metalhydroxide such as potassium hydroxide, for example in an aqueousalcoholic medium such as aqueous ethanol. The product may then beisolated directly as carboxylate salt or, where desired, treatment withacid is used to allow isolation of the product as the free acid (or evenby subsequent treatment with base as another type of salt).

3. Decarboxylation may conveniently be effected on standing at ambienttemperature for compounds in which the carboxylic acid group is attachedto nitrogen or by heating an appropriate salt of the acid if this groupis attached to carbon.

4. Mild oxidation may conveniently be effected by treatement with anoxidizing agent such as mercuric oxide or ferric chloride and strongeroxidation with other selected oxidizing agents such as selenium, forexample for the aromatization of dihydro- and tetrahydrobenzenes.

5. The modification ##STR15## wherein S and T are as hereinbeforedefined, may conveniently be effected by reaction with a compoundH--S--T. Thus, for example the reaction --CO₂ alkyl→--CONHNHR² employshydrazine when R² =H or a substituted hydrazine NH₂ NHR² in other cases.

6. The modification ##STR16## may conveniently be effected by a reactionwith an alcohol or mercaptan containing the desired alkyl group which ispresent in the group R₁. Thus, for example the reaction ##STR17##employs an alcohol (alkyl--OH) as the reagent whilst the reaction##STR18## employs a mercaptan (alkyl-SH) as the reagent. Reactions ofthis general type are well known in the literature, the conditionsinvolving reaction of the two reagents in the presence of a base, suchas pyridine, in the cold or with heating as necessary.

7. The modification --CO.NH.CO→--CO.N(CO₂ R).CO→--CO.N(D--CO₂ R¹).CO--may conveniently be effected by reacting the maleimide, or like adduct,with an ester of chloroformic acid, particularly the ethyl or especiallythe methyl ester in a procedure well known in the art for effectingsubstitution by an ester group, followed where desired by reaction withan amino acid, for example glycine and preferably in aqueous sodiumbicarbonate as a reaction medium, to effect replacement of the estergroup by the residue of the acid lacking the amino group, again in aprocedure well known in the art for effecting this type of reaction.

8. Alternatively the intermediate type of modification containing anester group may also be produced directly, for example by formation ofthe Diels-Alder adduct with N-methoxycarbonylmaleimide, and the compoundso prepared may then be modified further by reaction with an amino acidas described above.

9. The modification ##STR19## may conveniently be effected by treatmentwith an aqueous base, for example aqueous sodium hydroxide, the productbeing isolated as the free di-acid or as a salt.

It will be appreciated that the reactions described above are not theonly ones which may be used for effecting the modifications to theDiels-Alder adducts and that various alternative reaction procedures maybe used as will be apparent from the art relating to reactions of thesame general type.

The various Diels-Alder adducts according to the present invention willgenerally, excepted as discussed hereinafter, infuence the distributionof aphids on plants in a similar fashion to (E)-β-farnesene. It is notcertain at the present time whether this activity arises from a releaseof (E)-β-farnesene in the field, from the retention of the activity ofthe parent compound in the derivatives themselves or from another cause.It is believed, however, that the primary cause of activity may dependon the particular type of Diels-Alder adduct. Thus with certaincompounds the primary cause of activity may arise from the occurrence ofa reverse 1,4-cyclo-addition reaction or retro Diels-Alder reaction, forexample: ##STR20## it is believed that the former, N-heterocyclic,system may be generated under field conditions from various relatedN-substituted systems. With other compounds, such as the adducts withmaleic anhydride, diethyl maleate and diethyl acetylene 1,2-dicarboxylicacid, the primary cause of activity may well result from the activity ofthe compound as such. A particular advantage of the present inventionlies in the variety of Diels-Alder adducts which may be prepared from(E)-β-farnesene, thus enabling a compound having the best properties fora particular situation, in terms of solubility and compatibility withplants or other pest control agents, etc., to be selected. Among theadducts described hereinbefore derivatives capable of generating a3,6-dihydropyridazine structure or especially derivatives having asulpholene structure are preferred when release of (E)-β-farnesene assuch is desirable but, where this is not necessarily required, theadducts with diethyl maleate and diethyl acetylene 1,2-dicarboxylate andrelated compounds are of particular value.

The alarm activity of (E)-β-farnesene and of the derivatives of thepresent invention is effective for many aphid species, for example Myzuspersicae (Sulz.) although there are some species where little activityis shown, for example Brevicoryne brassicae(L.), Aphis sambuci(L.) andHyalopterus pruni(Geoffroy). Aphid control is required in relation to awide variety of crops including Angiosperms, Gymnosperms, etc. Thepresent invention is thus applicable to arable, orchard andhorticultural crops including particularly beet, potatoes, cereals suchas wheat and barley, beans, hops, cotton and various fruit crops. Thederivatives may be formulated in various ways, depending on theparticular use as discussed hereinafter, usually by conventionalprocedures. However, they are often applied together with some form ofdiluent or carrier. The present invention thus includes a pest controlcomposition comprising an (E)-β-farnesene derivative which is obtainableas a Diels-Alder adduct of (E)-β-farnesene and a dienophile or bymodification of such an adduct in a manner as defined hereinbeforetogether with a diluent or carrier.

Various types of diluents or carriers suitable for agriculturalapplications, particularly to plants, may be used including aqueousformulations, oily formulations, etc. One type of formulation ofparticular interest is as an emulsion in water which may, if desired,employ emulsifying agents, particularly non-ionic surface active agentsand especially those based on a polyether structure, for examplepolyoxyethylene stearate and nonylphenylpolyoxyethylanol. An alternativetype of formulation is microencapsulation, for example in a polyureacapsule, since the derivatives, although more stable than(E)-β-farnesene itself, may benefit from some protection against aerialoxidation, particularly in certain of their uses described hereinafter.For this reason, it may also be worthwhile including an antioxidant, forexample an N-phenyl-N'-alkyl-p-phenylenediamine or B.H.T. inmicroencapsulated or other formulations. It will be appreciated,however, that ultra low volume techniques may enable one to reduce oreven dispense with the use of a diluent or carrier.

One of the main areas of use of compounds according to the presentinvention in pest control involves their use as an aphid dispersant inconjunction with a pesticidal (aphicidal) spray in order to increasecontact of the aphid with the toxicant through the increased movement ofthe aphids on the crop. Such a procedure most usually involvesapplication, to a crop on which aphids are present or which they may beexpected to infest, of the (E)-β-farnesene derivative followed shortlythereafter by a pesticide composition. A wide variety of pesticides maybe used including particularly pyrethroid pesticides, for examplepermethrin, organophosphorus pesticides, for example malathion, orfenitrothion and some carbamates, for example carbaryl, etc. In order tobe advantageously used in conjunction with the derivatives the pesticidewill usually be required to have some degree of contact action. Thus,the systemic activity of pesticides or the translaminar or fumigantaction of compounds such as pirimicarb, will not normally be enhanced bythe use of repellant or dispersant derivatives. Only in the exceptionalcase of derivatives such as the Diels-Alder adduct between(E)-β-farnesene and di-octadecyl acetylene dicarboxylate which showarrestant activity may this activity be utilised in increasing contactbetween aphids and a systemic pesticide with which a crop has beentreated. The action of pesticides having both systemic and contactactivity, for example dimethoate, should be improved by the use of themajority of compounds according to the present invention which have adispersant action. Indeed, the enhancement of the contact action ofpesticides which is produced by the use of dispersant compounds mayenable the use of contact pesticides which are not normally sufficientlyactive for use as aphicides. Such dispersant compounds may also enhancethe action of other pest control agents such as adhesives, hormones andbiological agents including viruses, bacteria, parasitoids, parasitesand predators. This has the advantage of bringing into use pesticidesand other agents to which aphids have not the opportunity to develop anysignificant level of resistance as they have to some of the commonlyused systemic aphicides.

The period between application of the derivative and the pesticide canbe quite short, not normally being longer than about 15 minutes, and oneconvenient mode of application involves the use of a tractor with a boomat the front which dispenses the derivative and one at the back whichdispenses the pesticide composition. Providing the two are compatible itis also possible to apply the derivative and pesticide mixed in a singlecomposition.

Accordingly the present invention further comprises a method of aphidcontrol which comprises applying to a crop an (E)-β-farnesene derivativeas described hereinbefore in conjunction with a pesticide.

It is even possible to combine (E)-β-farnesene activity and pesticidalactivity in one compound, for example in the organophosphorus compoundsof the form. ##STR21## wherein X, R₁, R₂, R₃ are as definedhereinbefore. Such compounds may be employed in the pesticidal controlof aphids either with or without the associated use of a separatepesticide.

Since the particular use just described of the (E)-β-farnesenederivatives in aphid control utilises the activity of the derivativequite rapidly after it is applied, stability considerations are notquite as important as in the other main areas of use describedhereinafter. It is possible, therefore, in this usage to consider theuse of (E)-β-farnesene itself, most conveniently dispensed as a vapourin a stream of nitrogen or air. A suitable rate of application isconveniently about 5 to 1000 mm/second, for example about 230 mm/second.The present invention thus extends to the use of (E)-β-farneseneprepared as described hereinbefore in aphid control as well as toprovide a starting material for the preparation of derivatives accordingto the present invention.

A further main area of use of (E)-β-farnesene derivatives according tothe present invention involves their use in the control of aphidbehaviour per se as opposed to when associated with their destruction.Since this use, unlike that just described, requires activity to besustained over an extended period, the derivatives of the presentinvention are much more suited to it than (E)-β-farnesene itself and itrepresents the most important aspect of the use of these derivatives inaphid control. The settling and larviposition of aphids on plants leadsto damage of those plants through (a) feeding, (b) moulds growing on thehoney dew formed by aphids, and (c) injection of xenobiotics from aphidsaliva during feeding and sampling which causes distorted plant growth,etc., and the application to plants of the derivatives will control orprevent such damage. A further area of use of the derivatives in thecontrol of crop damage lies in the control of virus transmission byaphids. Apart from the type of damage described above caused by aphidssettling on crops, the feeding, and the sampling by the insects whichprecedes feeding, also produce crop damage by encouraging the spread ofany virus infection present within the crop. Thus, for example, thesemi-persistent beet yellow virus and the non-persistent potato virus Yare normally acquired very rapidly by aphids such as Myzus persicae andtransmitted by them. Application of the derivatives to plants throughinfluencing aphid behaviour as described above will also prevent orcontrol such transmission and represents a very important use of thepresent invention.

Accordingly the present invention further comprises a method for thecontrol of crop damage by aphids which comprises applying to a crop an(E)-β-farnesene derivative as described hereinbefore. It will beappreciated that, if desired, the derivatives may be administered inadmixture with or in conjunction with other crop damage control agentsincluding certain pyrethroids that control virus transmission by aphids,or indeed with any other types of agricultural agent with which theiruse can conveniently be combined.

Treatment of a crop with an (E)-β-farnesene derivative according to thepresent invention is of value for the control of crop damage which itwill achieve. However, where the derivative is one such as is discussedabove which also shows aphid toxicity, for example an organo phosphoruscompound, then control is exerted in two ways, i.e. both through controlof damaging aphid activity and through aphid destruction. With thosederivatives not possessing a toxic action in their own right it ispreferred, whilst applying the derivative to the crop, to take theopportunity of also applying a pesticide either concomittantly with orimmediately after the derivative. Whilst, as indicated above, such apesticide preferably has some contact action, it is of course possibleto apply a systemic pesticide whilst applying the derivative althoughthe latter will, unless one of the attractant compounds according to thepresent invention is employed, then function substantially only throughcontrol of crop damage rather than also through enhancement of theeffect of the pesticide.

The (E)-β-farnesene derivatives of the present invention may be appliedto crops using standard techniques or newly developed methods.Application may be made before or following infestation of the crop.Electrostatic spraying is one existing technique which is of particularinterest for the application of the derivatives to crops. Thus, aphidsoften feed on the lower surfaces of leaves and electrostatic sprayingwill achieve improved coverage of such parts of the plant. With many ofthe compounds of the present invention only a contact effect is presentso that good coverage of the plant is important. With certain compounds,however, and particularly those of formula (8) a level of systemicactivity may also be present so that the compound is translocatedthrough a plant to areas other than those directly contacted by thecompound. Whilst crop application levels will depend on the particularderivative used and on the particular use being made of it, it may bestated as a guide that a rate of application to crops from about 10 mgto 1 kg/ha, conveniently 100 mg to 100 g/ha, for example 300 mg/ha isoften suitable. These rates are applicable whether the derivative isapplied alone or with a pesticide. The pesticides may conveniently beapplied at conventional dosage rates.

The (E)-β-farnesene derivatives of the present invention, in view oftheir structural similarities to the juvenile hormones, are also ofinterest for the control of pests other than aphids, particularly otherinsects such as the holometabolous insects. Broadly similar techniquesmay then conveniently be used to those described above in relation toaphid control. Moreover, it is possible that the compounds may exertbeneficial effects in pest control and over the virus infection ofplants through mechanisms additional to those specifically discussedabove.

The invention is illustrated by the following examples.

It will be seen that the various Diels-Alder adducts are prepared from(E)-β-farnesene which is in admixture with a minor amount of(Z)-β-farnesene. The various active adducts containing an(E)-(4,8-dimethyl-3,7-nonadienyl) group are the therefore obtained inadmixture with the corresponding adduct containing(Z)-(4,8-dimethyl-3,7-nonadienyl) group having the cis rather than thetrans configuration about the double bond joining the 3 and 4 positions.It will be appreciated that either such cis compounds are an inactivebut quite acceptable contaminant of the trans compounds or, as indicatedabove, contribute some worthwhile activity to the mixture.

EXAMPLES Example 1 Preparation of (E)-β-farnesene

The preparation is carried out using glass Quickfit type apparatuscomprising a column having a sinter at the base thereof and which issurrounded by a heating coil. At the top of the main column is arrangeda dropping funnel with a bypass tube and above this funnel is a smallcolumn on top of which is fitted a vacuum gauge and at the side of whichis a downwardly pointing tapped take off terminating in a small roundbottomed flask. At the bottom of the main column is an air cooled traphaving a take off to a pump. Neutral alumina (50 g) is placed in themain column and is heated to 200° C. under a vacuum (0.1-0.2τ) providedby a rotary pump. Pyridine (4 g) from the round bottomed flask isallowed to evaporate and pass through the bypass tube and then throughthe column. Nerolidol (80 g, commercial material containing (E) and (Z)isomers) is then allowed to drip from the dropping funnel into thecolumn during a period of 4.5 hours. The product which is collected as alight brown liquid (69.5 g) in the air cooled trap below the column ischromatographed on Florisil (200 g) with hexane. Removal of the hexaneunder vacuum gives a straw coloured liquid (68.7 g, containing 67% oftheoretical yield of β-farnesenes), which consists predominantly of amixture of (E)- and (Z)-β-farnesene and contains 47% w/w of(E)-β-farnesene and 23% w/w of (Z)-β-farnesene. The final product issealed under nitrogen in batches (10 mg and 1 g) in glass ampoules.

Example 2 Preparation of Diels-Alder adduct between (E)-β-farnesene anddiethyl azodicarboxylate (I)

A solution of the (E)-β-farnesene-containing product of Example 1 (14.5g) in ether (20 ml) is cooled to -20° C. and diethyl azodicarboxylate(8.7 g) is slowly added with stirring. The mixture is stored at -20° C.overnight and then at 4° C., the reaction being shown by n.m.r. to becomplete after 8 hours at 4° C. The mixture is then subjected tofractional distillation to give the adduct,1,2-bis(ethoxycarbonyl)-4-(4,8-dimethyl-3,7-nonadienyl)-1,2,3,6-tetrahydropyridazine(I) as a yellow oil (8 g, 43%) 180°-185° C./0.3τ; n_(D) ²⁰ 1.4938; M⁺(m/z as % of base peak): 378(2.9); δ(CCl4) 1.30 (t, 6H), 1.70 (m, 9H),2.08 (m, 8H), 3.60-4.40 (m, 4H), 4.26 (q, 4H), 5.20 (m, 2H), 5.60 (br,t, 1H).

Example 3 Preparation of Diels-Alder adduct between (E)-β-farnesene andsulphur dioxide (II)

The (E)-β-farnesene containing product of Example 1 (17 g) and liquidsulphur dioxide are sealed in a glass ampoule and stored at ambienttemperature for 18 hours. The ampoule is opened after cooling and theexcess SO₂ is allowed to evaporate. The residue is then chromatographedon Florisil using sequentially hexane, an ether/hexane mixture ofincreasing concentration in ether, and finally ether, the effluent beingmonitored by n.m.r. Removal of the solvent under vacuum from theappropriate fractions gives 3-(4,8-dimethyl-3,7-nonadienyl) sulpholene(II) as a straw coloured liquid (9 g, 58%); n_(D) ²⁰ 1.5080; M⁺ (m/z as% of base peak): 268 (0.02); δ(CCl₄) 1.70 (m, 9H), 2.08 (m, 8H), 3.70(m, 4H), 5.16 (m, 2H), 5.78 (br, t, 1H). Note: On heating at 180° C.under a vacuum of 1τ the sulpholene regenerates an (E)- and(Z)-β-farnesene mixture in high yield.

Example 4 Preparation of1-ethoxycarbonyl-4-(4,8-dimethyl-3,7-nonadienyl)-1,2,3,6-tetrahydropyridazine(III)

The Diels-Alder adduct of Example 2 (4.0 g) is hydrolysed by placing itin a solution of potassium hydroxide (5.0 g) in water (5.0 g) andethanol (25.0 ml) for 4 days at room temperature. The resulting solutionis partitioned with water (25 ml) and light petroleum (60°/80°; 25 ml)and the aqueous phase is acidified with acetic acid and partitioned withlight petroleum (60°/80°; 25 ml). The light petroleum solution is dried(MgSO₄) and then concentrated to give the title compound (III) as ayellow oil (2.5 g, 77%); n_(D) ²⁰ 1.5022; M⁺ (m/z as % of base peak):306 (38.6); δ(CCl₄) 1.30 (t, 3H), 1.70 (m, 9H), 2.08 (m, 8H), 3.40 (m,2H, 3.96 (br, s, 2H), 4.22 (q, 2H),4.30 (br, t, 1H), 5.20 (m, 2H), 5.60(br, t, 1H).

Example 5 Preparation of1,2-bis-methyl-4-(4,8-dimethyl-3,7-nonadienyl)-1,2,3,6-tetrahydropyridazine(IV)

The Diels-Alder adduct of Example 2 (5.0 g) is added slowly to a stirredsuspension of lithium aluminium hydride (1.5 g) in dry ether (100 ml)and the mixture then refluxed for a further 0.5 hours. The excesshydride is destroyed by adding ethyl acetate and a granular precipitateis formed by adding, in turn, water (1.5 ml), 2N NaOH (1.5 ml) and water(4.5 ml). The precipitate is filtered off and the filtrate concentratedand distilled to give title compound (IV) as a yellow oil (3.1 g, 77%),b.p. 130°-5° C./0.3; n_(D) ²⁰ 1.5034; M⁺ (m/z as % of base peak): 262(100); δ(CCl₄) 1.70 (m, 9H), 2.08 (m, 8H), 2.34 (s, 6H), 3.10 (m, 4H),5.20 (m, 2H), 5.47 (br, t, 1H).

Example 6 Preparation of Diels-Alder adduct between (E)-β-farnesene andmaleic anhydride (V)

The (E)-β-farnesene-containing product of Example 1 (6.0 g) and maleicanhydride (2.0 g) in carbon tetrachloride (20 ml) are reacted togetherat 25° C. for 2 hours. The mixture is then distilled under reducedpressure to give 4-(4,8-dimethyl-3,7-nonadienyl)cyclohex-4-ene-1,2-dioic anhydride as a yellow oil (3.5, 70%;b.p.176°-182° C./0.25τ; n_(D) ²⁰ 1.5907; M⁺ (m/z as % base peak): 302(2.3): δ(CCl₄) 1.70 (m, 9H), 2.08 (m, 8H, 2.20-2.70 (m, 4H), 3.36 (m,2H), 5.16 (m, 2H), 5.70 (br, t, 1H).

Example 7 Preparation of Diels-Alder adduct between (E)-β-farnesene andacrolein (VI)

The (E)-β-farnesene-containing product of Example 1 (5.0 g) and acrolein(3.0 g) are heated together at 100° C. for two hours. The mixture isthen distilled under reduced pressure to give1-formyl-4-(4,8-dimethyl-3,7-nonadienyl)-cyclohex-4-ene as a yellow oil(2.2 g, 50%); b.p. 140°-150°/0.5τ; n_(D) ²⁰ 1.5033; M⁺ (m/z as % basepeak): 260 (3.6); δ (CCl₄) 1.70 (M, 9H), 1.90-2.30 (m, 15H), 5.16 (m,2H), 5.50 (br, t, 1H), 9.84 (br, s, 1H).

Example 8 Preparation of Diels-Alder adduct between (E)-β-farnesene andmethyl ethenyl ketone (VII)

The (E)-β-farnesene-containing product of Example 1 (6.0 g) and methylethynyl ketone (1.5 g) are heated together at 150° C. for 16 hours. Themixture is then distilled under reduced pressure to give1-acetyl-4-(4,8-dimethyl-3,7-nonadienyl)-cyclohex-4-ene as a pale yellowoil (2.3 g, 50%); b.p. 130°-140° C./0.2τ, n_(D) ²⁰ 1.4998; M⁺ (m/z as %of base peak): 274 (3.0; δ(CCl₄) 1.70 (m, 9H), 2.00-2.80 (m, 15H), 2.22(s, 3H), 5.20 (m, 2H), 5.50 (br, t, 1H).

Example 9 Preparation of Diels-Alder adduct between (E)-β-farnesene anddiethyl maleate (VIII)

The (E)-β-farnesene-containing product of Example 1 (10 g) and diethylmaleate (5.0 g) are heated together at 180° C. for two hours. Themixture is then distilled under reduced pressure to give1,2-bis-(ethoxycarbonyl)-4-(4,8 dimethyl-3,7-nonadienyl) cyclohex-4-eneas a pale yellow oil (8.5 g, 75%); b.p. 175°-180° C./0.3τ; n_(D) ²⁰1.4894; M⁺ (m/z as % of base peak): 376 (6.6); δ(CCl₄) 1.24 (t, 6H),1.70 (m, 9H), 2.08 (m, 8H), 2.36 (m, 4H), 2.80 (m, 2H), 4.14 (q, 4H),5.20 (m, 2H), 5.40 (br, t, 1H).

Example 10 Preparation of Diels-Alder adduct between (E)-β-farnesene anddidecyl ester of acetylene carboxylic acid (IX)

The (E)-β-farnesene-containing product of Example 1 (3.0 g) and thedidecyl ester of acetylene dicarboxylic acid (4.0 g) are heated togetherat 80° C. for two hours. The mixture is then chromatographed on Florisil(100 g), eluting with increasing concentrations of ether in hexane, togive1,2-bis(decyloxycarbonyl)-4-(4,8-dimethyl-3,7-nonadienyl)-cyclohexa-1,4-dieneas a pale yellow oil (6.3 g, 62%); n_(D) ²⁰ 1.4877; M⁺ (m/z as % of basepeak): 598 (3.0); δ(CCl₄) 0.92 (t, 6H), 1.30 (m, 32H), 1.70 (m, 9H),2.08 (m, 8H), 3.00 (m, 4H), 4.23 (q, 4H), 5.20 (m, 2H), 5.53 (br, t,1H).

Example 1 Preparation of further Diels-Alder adducts between(E)-β-farnesene and other maleic acid and acetylene dicarboxylic aciddiesters

(E)-β-farnesene is reacted with various diesters of maleic acid andacetylene dicarboxylic acid (obtained commercially or prepared bystandard esterification procedures from the appropriate acid andalcohol, for example by heating together and removing the watercontinuously as it is formed) in an analogous fashion to that describedin Examples 9 and 10, respectively, using a reaction temperature of 180°C. and a time of 2 hours for the maleic acid esters and of 80°-90° C.and 2 hours for the acetylene dicarboxylic acid esters. Compound X isdistilled but the other compounds are purified by chromatography as inExample 10.

Data relating to the various compounds of formula (11) are shown inTable 1 below, the values for compounds VIII and IX also being includedfor completeness [all of the compounds possess n.m.r. spectra in keepingwith their structure (11)]. ##STR22## (X is a4,8-dimethyl-3,7-nonadienyl group, Y and Y" represent hydrogen incompounds VIII and XIII and the second bond of a carbon-carbon doublebond joining the positions to which they are attached in all of theother compounds, and R is as shown in Table 1).

                  TABLE 1                                                         ______________________________________                                                             Yield of                                                                      purified                                                                      compound                                                 COMPOUND             as % of   Refractive                                     No.   R                  theoretical                                                                             index                                      ______________________________________                                        --VIII                                                                              CH.sub.2 CH.sub.3  75        1.4894                                     X     CH.sub.2 CH.sub.3  60        1.5012                                     XI    (CH.sub.2).sub.7 CH.sub.3                                                                        46        1.4854                                     XII   (CH.sub.2).sub.8 CH.sub.3                                                                        56        1.4801                                     --XIII                                                                              (CH.sub.2).sub.9 CH.sub.3                                                                        46        1.4800                                     IX    (CH.sub.2).sub.9 CH.sub.3                                                                        62        1.4877                                     XIV   (CH.sub.2).sub.10 CH.sub.3                                                                       54        1.4857                                     XV    (CH.sub.2).sub.11 CH.sub.3                                                                       42        1.4821                                     XVI   (CH.sub.2).sub.13 CH.sub.3                                                                       41        1.4844                                     XVII  (CH.sub.2).sub.2 CH(CH.sub.3)(CH.sub.2).sub.3                                                    51        1.4621                                           CH(CH.sub.3)(CH.sub.2).sub.3 CH(CH.sub.3).sub.2                         XVIII (CH.sub.2).sub.8 CHCH(CH.sub.2).sub.7 CH.sub.3                                                   35        1.4834                                           (Zconfiguration)                                                        XIX   (CH.sub.2).sub.17 CH.sub.3                                                                       47        (1)                                        XX                                                                                   ##STR23##         52        1.4695                                     XXI   (CH.sub.2).sub.9 CHCH.sub.2                                                                      40        1.4943                                     ______________________________________                                         (1) mp. 34-36° C.                                                 

Example 12 Preparation of1,2-dicarboxy-4-(4,8-dimethyl-3,7-nonadienyl)-cyclohex-4-ene (XXII)

A mixture of the Diels-Alder adduct of Example 6 (0.45 g) and a solutionof sodium hydroxide (0.08 g, 2 eq) in water (45 ml) is stirred overnightto give the title compound (XXII) in the form of a solution of itsdisodium salt in water.

Example 13 Preparation of Diels-Alder adduct between (E)-β-farnesene andN-methoxycarbonylmaleimide (XXIII)

The (E)-β-farnesene-containing product of Example 1 (0.4 g) andN-methoxycarbonylmaleimide (0.2 g) are heated at 90° C. for 2 hours. Themixture is then chromatographed on Florisil (10 g) in hexane, elutingwith increasing concentrations of ether in hexane, and the appropriatefractions of eluate evaporated to yieldN-methoxycarbonyl-5-(4,8-dimethyl-3,7-nonadienyl)-Δ⁴-tetrahydrophthalimide as a pale yellow oil (0.22 g, 47%). NOTE: As analternative to using this compound in a modification of type 8 describedhereinbefore, or to using a modification of type 7 describedhereinbefore, compounds containing a group --D--CO₂ R¹ as described inmodification 7), for exampleN-carboxymethyl-5-(4,8-dimethyl-3,7-nonadienyl-Δ⁴-tetrahydrophthalimide, may be prepared directly through a Diels-Alderreaction with a maleimide N-- substituted by a group --D--CO₂ R¹, forexample with N-carboxymethyl maleimide which is accessible by reactionsdescribed in the art, such as those discussed under modification 7 for asequence --NH--→--N(CO₂ R)--→--N(D--CO₂ R¹)--.

Example 14 Activity of (E)-β-farnesene on the settling of aphids

(A) Air (20 ml) from a glass syringe containing a freshly broken ampouleof the (E)-β-farnesene-containing product of Example 1 (10 mg) was blownduring a period of 10 seconds at colonies of various types of feedingaphids (ca 20) situated 1 cm from the tip of the syringe needle. Thenumber of aphids that moved within 60 seconds was determined for 7replicates, the results being given in Table 2 below as the percentageof the total number of aphids which moved within this period.

                  TABLE 2                                                         ______________________________________                                                            Response                                                  Aphid               (% ± standard error)                                   ______________________________________                                        Myzus persicae (Sulz.)                                                                            99 ± 0.6                                               Aphis fabae Scop.   71 ± 5.8                                               Phorodon humuli (Schrank)                                                                          78 ± 10.2                                             Sitobion avenae (Fab.) (green)                                                                     31 ± 11.7                                             Rhopalosiphum padi (L.)                                                                           47 ± 4.8                                               Nasonovia ribis-nigri (Mosley)                                                                    88 ± 5.9                                               Metopolophium dirhodum (Walk.)                                                                    61 ± 8.3                                               ______________________________________                                    

(B) Nitrogen (3 liters) was passed through a vessel containing a freshlybroken ampoule of the (E)-β-farnesene-containing product of Example 1 (1g) absorbed onto filter paper and the nitrogen was then blown at 230mm/sec at 16 large plants of Brassica pekinensis infested with the aphidMyzus persicae. Over 90% of the aphids began to move about the plantsafter application of the (E)-β-farnesene.

Example 15 Activity of (E)-β-farnesene derivatives on the settling ofaphids

The (E)-β-farnesene derivatives I to X and XIII were emulsified withwater at 1% and 0.5% w/v concentration using 0.1% w/v of Ethylan BV asemulsifying agent and the emulsion was painted onto one half of aBrassica pekinensis leaf. The other half of the leaf was treated withemulsifier and water only. Aphids (Myzus persicae, ca 20) were placed onthe leaf and their escape prevented by enclosing the leaf between twopetri dishes. After 24 hours, the numbers of aphids settled on the twoleaf halves were counted for 10 replicates. The results are given inTable 3 and show the numbers of aphids on the treated and control halvesof the leaf for each derivative together with the statisticalsignificance of difference, P.

                  TABLE 3                                                         ______________________________________                                        Number of aphids settled                                                                           Statistical significance                                 control/treated      of difference, P .sub.--                                 Compound                                                                              1% conc.  0.5% conc  1% conc 0.5% conc                                ______________________________________                                        I       11.4/3.6   9.8/8.6   <0.001  ns                                       II      15.5/2.5   9.7/8.3   <0.001  ns                                       III     15.9/2.8  10.7/6.5   <0.001  <0.05                                    IV       9.4/2.3  12.2/4.6   <0.01   <0.01                                    V       13.4/1.6  13.6/3.3   <0.001   <0.001                                  VI       9.6/5.6  10.4/5.1   <0.01   <0.01                                    VII     14.4/1.9  13.2/4.2   <0.001  <0.01                                    VIII    11.3/1.8  12.7/6.0   <0.01   <0.01                                    IX      14.1/3.0  13.4/3.8   <0.001   <0.001                                  X       14.5/3.9   8.3/9.0   <0.001  ns                                       XIII    16.1/2.6  12.2/5.4   <0.001  <0.01                                    ______________________________________                                    

The symbol ns indicates that, at that concentration, the results withthe compound were not statistically different from those with thecontrol. It will be seen therefore that all of the compounds showsignificant activity at 1% and most also show such activity at 0.5%.

The same procedure was carried out with the (E)-β-farnesene derivativesIX to XII and XIV to XIX at 0.5%, 0.1% and 0.05% w/v concentration. Theprobability values are shown in Table 4. In general, when differenceswere not statistically significant, experiments with that compound werenot conducted at lower concentrations.

                  TABLE 4                                                         ______________________________________                                                Statistical significance of difference, P .sub.--                     Compound  0.5% conc   0.1% conc 0.05% conc                                    ______________________________________                                        X         ns                                                                  XI        <0.01       ns                                                      XII       <0.01       <0.05                                                   IX         <0.001     <0.001    ns                                            XIV        <0.001     <0.001    <0.05                                         XV        ns                                                                  XVI       <0.01                                                               XVII      ns                                                                  XVIII     <0.01       ns                                                      XIX.sup.(1)                                                                             <0.05       ns                                                      ______________________________________                                         .sup.(1) This compound was observed to give an aggregatory rather than a      dispersant effect.                                                       

The symbol ns has the same meaning as in Table 3. It will be seen thatthe highest level of activity is to be found in the compounds containingan OR group of nine, ten or eleven carbon atoms, the level of activitybeing observed to increase with increasing carbon number for these threecompounds. Reference to Table 3 shows that in the case of the C₁₀compounds, the compound in which the six membered ring contains twodouble bonds (IX) is more active than that in which only one double bondis present (XIII).

Example 16 Activity of (E)-β-farnesene derivatives on the transfer ofviruses by aphids

On pages 49 to 54 of volume 100 of the Annals of Applied Biology (1982)Gibson, Rice and Sawicki describe insecticide susceptible (S) andinsecticide resistant (R₁ and R₂) clones of M. persicae as well asclones of the non-persistent potato virus Y (PVY) and thesemi-persistent beet yellow virus (BYV). Gibson et al also describe alaboratory test for assessing the effects of compounds on virus uptakeby the apterae of M. persicae and this procedure was applied tocompounds I, II, III, IV, V, VI, VIII, IX, X and XIII as describedhereinbefore in the Examples. Aphids were confined on half-leavestreated either with an emulsion (generally at 1% w/v) of the compoundprepared using 0.1% w/v of Ethylan BV or with water containing theemulsifier only. Confinement on the leaves was for a period of 4 hourswhen testing for BYV acquisition and for 2.5 minutes when testing forPVY acquisition. To detect for virus acquisition the aphids weretransferred to indicator seedlings and the number of plants infected bytest and control aphids were compared.

The results are presented in Tables 5 and 6 where they are given as thedifference from the control in percentage terms (a value of -25%indicating a reduction to three-quarters of the control figure and -75%indicating a reduction to one-quarter of the control figure). It will beseen that in the case of Table 5, relating to tests on the BVY virus,results for settling and nymph production are quoted as well as forvirus infected plants.

It will be seen that some level of control of the transfer of virus wasgenerally effected by the compounds and in Table 6 the control resultswere calculated to be statistically significant except in the one caseutilising a 0.01% w/v concentration where a result was obtained for Pwhich was not statistically significant (ns).

                  TABLE 5                                                         ______________________________________                                        Acquisition of BVY by the R1 resistant strain of Myzus persicae               Com-   Percentage difference from control                                     pound.sup.(1)                                                                        Settling Nymph production                                                                             Virus infected plants                          ______________________________________                                        II     -68      -89            -75                                            I      -23      -81            -58                                            VIII   -10      -33            -22                                            V      -38      -73            -32                                            X      -15      -45            -10                                            III    -31      -62            -71                                            I      -22      -82            -6                                             VIII   -29      -76            -23                                            V      -2       -36            +12                                            X      -53      -68            -52                                            VI     -11      -51            -2                                             XIII   -41      -64            -26                                            IX     -47      -96            -60                                            III    -2       -23            -4                                             IV     leaves                                                                        destroyed                                                              ______________________________________                                         .sup.(1) On tests of the first group the compound was applied to the          leaves as a 1% w/v solution just before the test whilst in tests of the       second group the compound was similarly applied but 24 hours before the       test.                                                                    

                  TABLE 6                                                         ______________________________________                                        Acquisition of PVY by the S susceptible strain and R1 and R2                  resistant strains of Myzus persicae                                                  Virus infected plants -                                                                      Statistical significance                                       percentage difference                                                                        of difference for com-                                         from control   bined results                                           Compound.sup.(1)                                                                       S        R1      R2    P .sub.--                                     ______________________________________                                        V        -57      -77     -96   <0.001                                        X        -20      -65     -42   <0.001                                        IX        -100    -97     -96   <0.001                                        IV       -56      -75     -68   <0.001                                        IX       -95      -92     -78   <0.001                                        IX       -95      -93     -92   <0.001                                        IX       -39      -42     -19   <0.05                                         IX       +12      +12     +12   ns                                            ______________________________________                                         .sup.(1) In tests of the first group the compound was applied to the          leaves as a 1% w/v solution just before the test, except for compound IX      which was similarly applied seven days before the test. In the tests of       the second group, which were run con currently, compound IX was applied t     the leaves just before the test at a concentration of 1% w/v, 0.1% w/v or     0.01% w/v (the results being given in descending order for descending         concentration).                                                          

Example 17 Systemic activity of (E)-β-farnesene derivatives on thesettling of aphids

Compounds V and XXII were tested, at 0.5% w/v concentration in the caseof V and at 0.05% and 0.01% w/v in the case of XXIV, for systemic aphidsettling activity by the following procedure. Leaves of Brassicapekinensis were severed from the plant under water to prevent air fromentering the stem and the leaves were then split down the middle fromthe tip to halfway along their length. The leaves were then arranged inoverlapping pairs through the positioning of the tip of one leaf halfwayalong the second with half of the upper part of the first leaf beingarranged above the upper part of the second leaf and the other half ofthe upper part of the first leaf being arranged below the upper part ofthe second leaf through superimposing the splits present in each leaf.Once so positioned, the coincident splits in the two leaves were sealedlengthwise with Bluetack.

The pairs of leaves were then arranged with the stem of one leaf in thetest solution and the stem of the other leaf in water and were allowedto remain like this for several hours (preliminary studies with red inkconfirming that this procedure allows an even distribution throughoutthe leaf to occur). Once uptake had occurred, a petri dish containing 20Myzus persicae apterae was placed above the upper halves of the twoleaves, the dish thus covering an equal area of control and treatedleaf. The number of aphids on each leaf were counted after 24 hours.

It was found that compound V used in this way exerted a phytotoxiceffect at 0.5% w/v whilst compound XXII exerted a phytotoxic effect atthis concentration and at 0.1% w/v. In order to be able to study theeffect of compound XXII at 0.1% w/v concentration without thecomplication of phytotoxicity, the above procedure was used but with theleaves being retained on the plants and the plant roots being immersedin the test solution or water.

The results obtained are shown in Table 7, averaged over 10 replicates,where it will be seen that statistically significant evidence ofsystemic effect was obtained for compound XXII at 0.05% w/v and at 0.1%w/v (ns indicates a non-statistically significant result).

                  TABLE 7                                                         ______________________________________                                                Concen-  Number of aphids                                                                           Statistical significance                                tration  settled control/                                                                           of difference                                   Compound                                                                              % w/v    treated      P .sub.--                                       ______________________________________                                        V       0.5      10.5/7.9     ns                                              XXII    0.05     11.5/4.5     <0.05                                           XXII    0.01      8.7/8.3     ns                                              XXII    0.1.sup.(1)                                                                            10.8/3.8     <0.05                                           ______________________________________                                         .sup.(1) Roots in test solution or water for control.                    

We claim:
 1. A compound of the formula ##STR24## wherein X is4,8-dimethyl-3,7-nonadienyl, Y, Y', Y" and Y'" are each hydrogen or anytwo of these which are adjacent form the second double bond of acarbon-carbon double bond joining the positions to which they areattached and the other two are hydrogen; R and R' are the same ordifferent and each is unbranched or branched alkyl or alkenyl of up to18 carbon atoms; V is --(CH₂ CH₂ O)_(n') H wherein n' is 1 to 10; W isthe same or different --(CH₂ CH₂ O)_(n') H wherein n' is as abovedefined, or is unbranched or branched alkyl or alkenyl of up to 18carbon atoms; and R¹ and R² are each hydrogen or one is hydrogen and theother is unbranched or branched alkyl or alkenyl of up to 18 carbonatoms.
 2. A compound according to claim 1 wherein R and R' areunbranched alkyl of 8 to 14 carbon atoms.
 3. A compound according toclaim 1 wherein R and R' are unbranched alkyl of 8 to 12 carbon atoms.4. A compound according to claim 1 wherein R and R' are unbranched alkylof 9 to 11 carbon atoms.
 5. A compound according to claim 1 of theformula ##STR25## wherein X is 4,8-dimethyl-3,7-nonadienyl, Y, Y', Y"and Y'" are each hydrogen or any two to these which are adjacent formthe second bond of a carbon-carbon double bond joining the positions towhich they are attached and the other two are hydrogen, and R and R' areeach unbranched or branched alkyl or alkenyl of up to 18 carbon atoms.6. A compound according to claim 1 wherein R¹ and R² are each hydrogenand Y, Y', Y" and Y'" are each hydrogen or Y' and Y'" are hydrogen and Yand Y" together form the second bond of a carbon-carbon double bond. 7.A compound according to claim 5 of the formula ##STR26## wherein X is4,8-dimethyl-3,7-nonadienyl and R and R' are each unbranched or branchedalkyl or alkenyl of up to 18 carbon atoms.
 8. A compound according toclaim 1 of the formula ##STR27## wherein X is4,8-dimethyl-3,7-nonadienyl, Y, Y', Y" and Y'" are each hydrogen or anytwo of these which are adjacent form the second bond of a carbon-carbondouble bond joining the positions to which they are attached and theother two are hydrogen, and R and R' are each unbranched or branchedalkyl or alkenyl of up to 18 carbon atoms.
 9. A compound according toclaim 8 wherein Y, Y', Y" and Y'" are each hydrogen or Y' and Y'" arehydrogen and Y and Y" together form the second bond of a carbon-carbondouble bond.
 10. A compound according to claim 1, in which R and R' areeach alkyl or alkenyl of eight to sixteen carbon atoms.
 11. A compoundaccording to claim 1, in which R and R' are each alkyl or alkenyl ofnine, ten or eleven carbon atoms.
 12. A compound according to claim 1,in which R and R' are each alkyl of up to 18 carbon atoms.
 13. Acompound according to claim 1, in which R and R' are each alkenyl of upto 18 carbon atoms.
 14. A compound according to claim 1, in which R andR' are each either unbranched or branched solely at the carbon atomattached to the group --CO₂ -- or --CO--.
 15. A compound according toclaim 1, in which R and R' are identical.
 16. A compound according toclaim 1 of the formula ##STR28## wherein X is4,8-dimethyl-3,7-nonadienyl, Y, Y', Y" and Y'" are each hydrogen or anytwo of these which are adjacent form the second bond of a carbon-carbondouble bond joining the positions to which they are attached and theother two are hydrogen, V is --(CH₂ CH₂ O)_(n') H in which n' is 1 to 10and W is the same or different --(CH₂ CH₂ O)_(n') H wherein n' is asabove defined, or unbranched or branched alkyl or alkenyl of up to 18carbon atoms.
 17. A compound according to claim 16 wherein Y, Y', Y" anY'" are each hydrogen or Y' and Y'" are hydrogen and Y and Y" togetherform the second bond of a carbon-carbon double bond.
 18. A compoundaccording to claim 16 wherein n' is 1 to
 6. 19. A compound according toclaim 18 wherein V and W are the same --CH₂ CH₂ O)_(n') H and n' is 2,3, or
 4. 20. A compound according to claim 1 which contains a4,8-dimethyl-3,7-nonadienyl group having the (E) configuration about thedouble bond at the 3,4 position.
 21. A compound according to claim 1wherein Y' and Y'" are each hydrogen, Y and Y" form the second bond of acarbon-carbon double bond joining the position to which they areattached and R and R' are each (CH₂)₁₀ CH₃.
 22. The compound accordingto claim 1 which is1,2-bis-(nonyloxycarbonyl)-4[(E)-4,8-dimethyl-3,7-nonadienyl]cyclohexa-1,4-diene,1,2-bis-(decyloxycarbonyl)-4-[(E)-4,8-dimethyl-3,7-nonadienyl]-cyclohexa-],4-diene,or1,2-bis-(undecyloxycarbonyl)-4-[(E)-4,8-dimethyl-3,7-nonadienyl]cyclohexa-1,4-diene.23. A pest control composition which comprises an effective amount of acompound of the formula ##STR29## wherein X is4,8-dimethyl-3,7-nonadienyl, Y, Y', Y" and Y'" are each hydrogen or anytwo of these which are adjacent form the second double bond of acarbon-carbon double bond joining the positions to which they areattached and the other two are hydrogen; R and R' are the same ordifferent and each is unbranched or branched alkyl or alkenyl of up to18 carbon atoms; V is --(CH₂ CH₂ O)_(n') H wherein n' is 1 to 10; W isthe same or different --(CH₂ CH₂ O)_(n') H wherein n' is as abovedefined, or is unbranched or branched alkyl or alkenyl of up to 18carbon atoms; and R¹ and R² are each hydrogen or one is hydrogen and theother is unbranched or branched alkyl or alkenyl of up to 18 carbonatoms, in combination with a suitable diluent or carrier.
 24. Acomposition according to claim 23 wherein the compound is of the formula##STR30## wherein X is 4,8-dimethyl-3,7-nonadienyl, Y, Y', Y" and Y'"are each hydrogen or any two of these which are adjacent form the secondbond of a carbon-carbon double bond joining the positions to which theyare attached and the other two are hydrogen, and R and R' are eachunbranched or branched alkyl or alkenyl of up to 18 carbon atoms.
 25. Acomposition according to claim 23 wherein R¹ and R² are each hydrogenand Y, Y', Y" and Y'" are each hydrogen or Y' and Y'" are hydrogen and Yand Y" together form the second bond of a carbon-carbon double bond. 26.A composition according to claim 24 wherein the compound is of theformula ##STR31## wherein X is 4,8-dimethyl-3,7-nonadienyl and R and R'are each unbranched or branched alkyl or alkenyl of up to 18 carbonatoms.
 27. A composition according to claim 23 which contains a4,8-dimethyl-3,7-nonadienyl group having the (E) configuration about thedouble bond at the 3,4 position.
 28. A composition according to claim 23in which R and R' are identical.
 29. A composition according to claim 24wherein Y' and Y'" are each hydrogen, Y and Y" form the second bond of acarbon-carbon double bond joining the position to which they areattached and R and R' are each (CH₂)₁₀ CH₃.
 30. A composition accordingto claim 23, in which R and R' are each alkyl or alkenyl of eight tosixteen carbon atoms.
 31. A composition according to claim 23, in whichR and R' are each alkyl or alkenyl of nine, ten or eleven carbon atoms.32. A composition according to claim 23, in which R and R' are eachunbranched or branched solely at the carbon atom attached to the group--CO₂ -- or --CO--.
 33. A composition according to claim 23 whichadditionally contains an effective amount of a pesticide.
 34. Acomposition according to claim 23 wherein the compound is1,2-bis-(nonyloxycarbonyl)-4-[(E)-4,8-dimethyl-3,7-nonadienyl]-cyclohexa-1,4-diene,1,2-bis-(decyloxycarbonyl)-4-[(E)-4,8-dimethyl-3,7-nonadienyl]-cyclohexa-1,4-diene,or1,2-bis-(undecyloxycarbonyl)-4-[(E)-4,8-dimethyl-3,7-nonadienyl]cyclohexa-1,4-diene.35. A method for the control of crop damage by aphids which comprisesapplying to a crop in need of protection from such damage an effectiveamount of a compound of the formula ##STR32## wherein X is4,8-dimethyl-3,7-nonadienyl, Y, Y', Y" and Y'" are each hydrogen or anytwo of these which are adjacent form the second double bond of acarbon-carbon double bond joining the positions to which they areattached and the other two are hydrogen; R and R' are the same ordifferent and each is unbranched or branched alkyl or alkenyl of up to18 carbon atoms; V is --(CH₂ CH₂ O)_(n') H wherein n' is 1 to 10; W isthe same or different --(CH₂ CH₂ O)_(n') H wheren n' is as abovedefined, or is unbranched or branched alkyl or alkenyl of up to 18carbon atoms; and R¹ and R² are each hydrogen or one is hydrogen and theother is unbranched or branched alkyl or alkenyl of up to 18 carbonatoms.
 36. A method according to claim 35 wherein the compound is of theformula ##STR33## wherein X is 4,8-dimethyl-3,7-nonadienyl, Y, Y', Y"and Y'" are each hydrogen or any two of these which are adjacent fromthe second bond of a carbon-carbon double bond joining the positions towhich they are attached and the other two are hydrogen, and R and R' areeach unbranched or branched alkyl or alkenyl of up to 18 carbon atoms.37. A method according to claim 35 wherein R¹ and R² are each hydrogenand Y, Y', Y" and Y'" are each hydrogen or Y' and Y'" are hydrogen and Yand Y" together form the second bond of a carbon-carbon double bond. 38.A method according to claim 36 the compound is of the formula ##STR34##wherein X is 4,8-dimethyl-3,7-nonadienyl and R and R' are eachunbranched or branched alkyl or alkenyl of up to 18 carbon atoms.
 39. Amethod according to claim 35 wherein the compound contains a4,8-dimethyl-3,7-nonadienyl group having the (E) configuration about thedouble bond at the 3,4 position.
 40. A method according to claim 35 inwhich R and R' are identical.
 41. A method according to claim 35 whereinY' and Y'" are each hydrogen, Y and Y" form the second bond of acarbon-carbon double bond joining the position to which they areattached and R and R' are each (CH₂)₁₀ CH₃.
 42. A method according toclaim 35, in which R and R' are each alkyl or alkenyl of eight tosixteen carbon atoms.
 43. A method according to claim 35, in which R andR' are each alkyl or alkenyl of nine, ten or eleven carbon atoms.
 44. Amethod according to claim 35, in which R and R' are each unbranched orbranched solely at the carbon atom attached to the group --CO₂ -- or--CO--.
 45. A method according to claim 35 wherein the compound is1,2-bis-(nonyloxycarbonyl)-4-[(E)-4,8-dimethyl-3,7-nonadienyl]-cyclohexa-1,4-diene,1,2-bis-(decyloxycarbonyl)-4-[(E)-4,8-dimethyl-3,7-nonadienyl]-cyclohexa-1,4-diene,or1,2-bis-(undecyloxycarbonyl)-4-[(E)-4,8-dimethyl-3,7-nonadienyl]-cyclohexa-1,4-diene.46. A method of aphid control which comprises applying to a crop in needof such control an effective amount of a compound of the formula##STR35## wherein X is 4,8-dimethyl-3,7-nonadienyl, Y, Y', Y" and Y'"are each hydrogen or any two of these which are adjacent form the seconddouble bond of a carbon-carbon double bond joining the positions towhich they are attached and the other two are hydrogen, R and R' are thesame or different and each is unbranched or branched alkyl or alkenyl ofup to 18 carbon atoms; V is --(CH₂ CH₂ O)_(n') H wherein n' is 1 to 10;W is the same or different --(CH₂ CH₂ O)_(n') H wherein N' is as abovedefined, or is unbranched or branched alkyl or alkenyl of up to 18carbon atoms; and R¹ and R² are each hydrogen or one is hydrogen and theother is alkyl or alkenyl of up to 18 carbon atoms, in combination withan effective amount of a pesticide.
 47. A method according to claim 46wherein the compound is of the formula ##STR36## wherein X is4,8-dimethyl-3,7-nonadienyl, Y, Y', Y" and Y'" are each hydrogen or anytwo of these which are adjacent form the second bond of a carbon-carbondouble bond joining the positions to which they are attached and theother two are hydrogen, and R and R' are each unbranched or branchedalkyl or alkenyl of up to 18 carbon atoms.
 48. A method according toclaim 46 wherein R¹ and R² are each hydrogen and Y, Y', Y" and Y'" areeach hydrogen or Y' and Y'" are hydrogen and Y and Y" together form thesecond bond of a carbon-carbon double bond.
 49. A method according toclaim 46 wherein the compound contains a 4,8-dimethyl-3,7-nonadienylgroup having the (E) configuration about the double bond at the 3,4position.
 50. A method according to claim 46 wherein the compound is1,2-bis-(nonyloxycarbonyl)-4-[(E)-4,8-dimethyl-3,7-nonadienyl]-cyclohexa-1,4-diene,1,2-bis-(decyloxycarbonyl)-4-[(E)-4,8-dimethyl-3,7-nonadienyl]-cyclohexa-1,4-diene,or1,2-bis-(undecyloxycarbonyl)-4-[(E)-dimethyl-3,7-nonadienyl]-cyclohexa-1,4-diene.51. A compound according to claim 5 of the formula ##STR37## wherein Xis 4,8-dimethyl-3,7-nonadienyl and R and R' are each unbranched orbranched alkyl or alkenyl of up to 18 carbon atoms.
 52. A compositionaccording to claim 24 wherein the compound is of the formula ##STR38##wherein X is 4,8-dimethyl-3,7-nonadienyl and R and R' are eachunbranched or branched alkyl or alkenyl of up to 18 carbon atoms.
 53. Amethod according to claim 36 wherein the compound is of the formula##STR39## wherein X is 4,8-dimethyl-3,7-nonadienyl and R and R' are eachunbranched or branched alkyl or alkenyl of up to 18 carbon atoms.